The formation of H atoms, following pulsed generation of CH2 a(1)A(1) in the presence of O-2, has been monitored by vacuum ultraviolet laser-induced fluorescence. The rise time of H is compatible with its production from the reaction of (CH2XB1)-B-3 + O-2, with the interaction between the singlet and O-2 leading exclusively to the formation of the triplet state by collision-induced intersystem crossing. A comparison of the intensities of the H atom signal from reaction of (CH2)-C-1 with H-2 and of (CH2)-C-1 with O-2 gives a yield of H from (CH2)-C-3 + O-2 of 0.8 +/- 0.2. (C) 2003 Elsevier Science B.V. All rights reserved.